Signaling system



J. C. FIELD.

SIGNALING SYSTEM.

APPLICATION FILED AUG-19, 191a.

' Patented Mar. 9, 1920.

Myer/"fan ../05 6 26 C. f7'e/a UNITED STATES PATENT ornron.

JOSEPII C. FIELD, OF ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF' NEW YORK, N. Y, A CORPORATION OF NEW YORK.

SIGNALING SYSTEM.

Patented Mar. 9, 1920.

Application filed August 1 9, 1918. Serial No. 250,538.

Orange, in the county of Essex, State of.

New Jersey, have invented certain new and useful Improvements in Signaling Systems,

of which the following is a full, clear, con'- cise, and exact description.

This invention relates to signaling systerns and more particularly to such systems in which selective signaling devices, located at local stations, may be operatively controlled over a single line circuit from a central station.

An object of this invention is the production of a system of this character in which alternating current selective signaling devices connected with the line circuit may be efiiciently and satisfactorily operated and in which one or more efiicient simplex'telegraph circuits may be provided for the transmission of telegraph messages thereover without interfering with the proper operation of the various selective signaling de vices connected with the line circuit.

In accordance with the various features of this invention a line circuit comprising a pair of line wires and joining a plurality of local or way stations and a central or despatchers station is divided into separate sections by means of low resistance high im pedance transformers or repeating coils for providing a plurality of simplex telegraph circuits on the one line circuit. With each section a plurality of way stations may be associated and at each of these stations there may be bridged across the line wires an al ternating current selector which is responsive to alternating current impulses transmitted over the line wires from the central station. At the central station there are provided condensers of suitable capacity, preferably taking the form of a plurality of V condensers equal in number to the number of local stations on the line circuit. In order that the best results may be obtained it is desirable that the capacity of the system balance the inductance thereof, and where the number of selectors connected with the line circuit may vary, it is very desirable although not absolutely necessary that the number of condensers at the central station be equal in number to the number of selectors connected with the line wires. In such cases the capacity of each condenser approximately balances the inductance of a selector. Then if a selector be removed from theline, only one of the condensers need be removed, or if an additional selector isadded to the system one more condenser may be connected in multiple with those at the central station. These condensers which are connected in parallel with respect to one another and in series with the line circuit take the place or those usually provided in series with the selectors at the several local stations.

This invention will be more fully understood from the following description when considered in connection with the accompanying drawing illustrating one embodiment thereof.

Referring to the drawing, 5 and 6 desig nate a pair of line wires with which are associated a central or transmitting station while localstations C and E are represented by' dotted rectangles. The apparatus shown above the dotted line 22 is located at the sending or transmitting station A.- At each of the local stations, there is a selectively operated signal controlling device comprising in general a polarized operating magnet 7, a step-by-stepelement8 carrying a' contact arm 9, and a stationary contact element 10. A centrally pivoted armature 12 is adapted, in response to alternating current impulses through the magnet 7, to advance the step-by-step element 8 into a position where the contact arm 9 will engage the contact element 10, in which position it is held. by means of a spoon-ended holding spring 14L engaging with a pin 15 in the step-by-' step element 8. For a more complete description of the selectively operated signal the line wires which includes impedance coils 18 and 19 (which are for protection against lightning discharge), answer back resistance 20, the windings of the vibrating bell 17, contact element 10, contact arm 9,

step-by-step element 8, pin 15 and holding spring 14 is alternately closed and opened to cause the transmission of an answer back signal to the central station A, where it is received in the receiver 22. The selector magnets 7 at each local station are connected in series with the impedance coils 18 and 19 in a bridge ofthe line wires 5 and 6.

Located at the central station A is a sending battery 30, the connection of which with the line wires 5 and 6 is controlled by a relay 31 and a pole changing relay 32 in energizing circuits controlled by a sending key comprising a rotatable toothed wheel 34 and contact springs 35 and 36. When the sending key is set in operation, contact spring 36 engages and remains in engagement with the toothed wheel 34 during the entire time the key is in operation, thereby maintaining relay 31 energized. Contact springs 35 and 36 intermittently engage during the operation of the key, thereby .in-'

termittently energizing the pole changing relay 32. In order to prevent undue sparking at the contacts of the pole changing relay 32, a condenser 37 and a resistance 38 are provided in bridge thereof. In like manner condenser 28 and resistance 29 connected in bridge of contact springs 35 and 36 prevent undue sparkingat these contacts. in order to prevent the selecting impulses from the sending battery 30 from inter-' fering with the proper operationof any telephone apparatus which may be connected with the line wires, there are provided impedance or retardation coils 39 and 40 in series with the line wires and a condenser 41 and a resistance 42 in bridge thereof which cooperate in a well-knownmanner to smooth out the sending impulses.

In order that the line wires 5 and 6 may be used to form one or more telegraph circuits between stations along the line, it is necessary that the line circuit be split up into as many sections as there are telegraph circuits desired. In the drawing, only two telegraph circuits are shown and these are obtained by introducing a repeating coil 50 into the line circuit, thereby dividing the line circuit into sections which are conductively separate to telegraph currents but inductively continuous to alternating current selecting impulses and to telephonic currents. At the telegraph station, intermediate the central station and the point where the repeating coil 50 is connected in the line circuit, there is provided across the line wires an inductive bridge comprising im-- pedance or inductance coils 51 and 52 and resistance coils 53 and 54, while at the telegraph station. beyond the repeating coil 50 there is provided across the line wires, an other inductive bridge comprising impech ance or inductance coils 55 and 56. A telegraph set 57 of the usual construction is connected between the middleof each inductive bridge and ground, whereby telegraph messages are transmitted over simplex circuits of the line wires. In order that these inductive bridges may offer but little resistance to the usual direct ciu'rent telegraph impulses traversing the simplex circuits, the windings of the impedance coils 51, 52, 55 and .56 and the windings of the repeating coil 50 are made of low resistance, each winding being preferably ofapproximately thirty ohms resistance. These inductive bridges are, of course, in shunt of the selector'magnets'Z, 7 so that it becomes necessary to prevent these inductive bridges from shunting the alternating current selecting impulses from the selector magnets. This is accomplishedby' making the inductive bridges of very high impedance, so that the short alternating current selecting impulses will not have time to build up inthese inductive bridges to shunt the selector operating. magnets. The impedance ofthe repeating coil windings is, of course, lower 31122111 the impedance of the retardation coils forming the simplex bridges, for the reason that it is necessary to repeat the selecting impulses into the next line section. This impedance is not so low as to interfere with the operation of the selectors.

Heretot'ore in systems employing alternating current selectors in bridge of line wires, it has been usual ,to connect a condenser in series with each selector. In the present system, if a condenser were con- 100 n'ected in series with each selector, false operation of the selector would result due to the fact that the inductive bridges would form discharge paths for the charged condensers at the cessation of the last of a se-.

station apparatus and to prevent an undesirable drain on the sending battery 30. These condensers 60 are shown connected in parallel with respect to one another and in series with the line wire 6. When charged with current of one polarity these condensers 11b assist the main sending battery upon the reversal of the polarity of current connected with the line circuit, thereby making it possible to use a lower voltage battery than would otherwise be possible. In other words, the capacity of the bank of condensers at the central station is such as to balance the inductance of the line with its selector bridges, whereby the required operating current through the selectors is oblar polarity is connected with the line cir-- a plurality of local stations, a repeating coilconnected in and dividing the line wires into inductively united sections, inductive bridges for the line wires, telegraph apparatus connected between ground and the middle point of each inductive bridge and each repeating coil winding, a selective sig-.

naling device connected in bridge of the line \vlres at each local station, and means including a condenser connected in one line wire at the central station for impressing impulses of opposite polarity upon the line wires for controlling the operation of the selective signaling devices.

In a signaling system, in combination, a pair of line Wires joining a central with a plurality of local stations, a repeating coil of low resistance ancthigh impedance connected in and dividing the line wires into inductively united sections, impedance coils of low resistance and high impedance connected in bridge of the line Wire sections, telegraph apparatus connected between ground and the middle point of each'impedance brid eand each repeating coil winding, a se ective signaling device connected in. bridge of the line Wires at each local station, and means including a condenser connected in one line wire at the central station for impressing impulses'of opposite polarity upon the line wires for controlling the operation of the selective signaling devices.

3. In a signaling system, in combination, a pair of line wires joining a central and a plurality of local, stations, inductive means connected in and dividing the line wires into inductively united sections inductive bridges for the line wires, signaling apparatus between the middle point of each inductive bridge and ground, selective signaling devices connected in bridge of the line wires, and means including a condenser, connected'in one line wire at the central station for impressing impulses of opposite polarity upon'the line wires and controlling the operation of the selective signaling devices.

In witness whereof I hereunto subscribe my name this 15th day of August, A. D. 1918.

JOSEPH oi FIELD. 

